A Single-Event Upset study has been carried out on PIN photodiodes from a range of manufacturers. A total of 22 devices of eleven types from six vendors were exposed to a beam of 63 MeV protons. The angle of incidence of the proton beam was varied between normal and grazing incidence for three data-rates (1.5, 2.0 and 2.5 Gb/s). We report on the cross-sections measured as well as on the detailed statistics of the interactions that we measured using novel functionalities in a custom-designed Bit Error Rate Tester. We have observed upsets lasting for multiple bit periods and have measured, over a large range of input optical power, a small fraction of errors in which an upset causes a transmitted zero to be detected as a one at the receiver.